2.081. a. Subject to the exceptions shown in Part 2, all TA personnel are required either to attend annual in camp training for a period of 15 continuous days, or alternative training or service as specified at paras 2.031, 2.085, 2.098, 7.055, and 7.076 unless authority has been granted for a lower training commitment as defined at para 2.036. (See para 2.004 for legal liabilities.)
b. Exceptionally for business or domestic reasons an individual may be granted authority to attend his unit camp for a reduced period of not less than 8 days. The balance to complete 15 days being made up by attending extra out of camp training.
c. Authority to attend a reduced unit camp, training or service in lieu of camp is to be shown on the CO â s Certificate of Efficiency and issued by the commanding officer by 30 April following a normal training year or 30 July following an extended training year. (See also para 2.058.)
You really should be able to find this out for yourself by looking at TA Regs on armynet.